The present invention relates to a photosensitive composition. The photosensitive composition of the present invention can be used, for example, as a photoresist in a lithography technology which is employed to produce electronic materials (semiconductor devices and the like).
For example, electronic materials in semiconductor devices and the like have been increasingly miniaturized. For example, a minimum processing size of a semiconductor integrated circuit device is now sub-half micron, i.e., within the range of less than about 0.5 .mu.m. Consequently, a lithography technology using a laser beam as an exposure light capable of fine processing, especially a KrF eximer laser lithography technology has attracted much attention.
With respect to a lithography technology capable of fine processing, for example, a KrF eximer laser lithography technology, a composition material containing a photosensitive compound is chiefly used which is photosensitized at a wavelength of 248 nm and which successively induces a reaction by the action of a substance formed through photosensitization like a catalyst. Such a photosensitive composition material is designated, for example, a chemical amplification-type resist.
This photosensitive composition material contains mainly a photosensitive acid generator which causes a reaction upon catalytically using an acid formed through light irradiation to give a light-irradiated portion a site soluble in a developer (in the case of a positive resist) or insoluble in a developer (in the case of a negative resist).
In this case, however, an acid is formed in a small amount, and is also instable. Meanwhile, a variety of substances are present in an environmental atmosphere (air or the like) or on a substrate to be processed, and include those having properties to inhibit a performance of an acid formed. For example, basic gases (ammonia gas, basic gases considered to derive from a plasticizer of a piping resin, and the like) deactivate an acid formed. Further, substances on a substrate sometimes become a catalyst poison to inhibit a performance of an acid. Illustrative examples may include, for example, ammonia or water adsorbed on a silicon nitride insulating layer on a substrate, metallic layers such as titanium nitride or coated substrates such as boron phosphorus silicate glass (BPSG) which is a coated glass, all of which may have a deactivating effect on an acid.
As stated above, in the conventional technology, the above-mentioned photosensitive composition intends to be deactivated with a basic substance such as an amine or the like in air, a catalyst poison on a substrate to be processed, or the like. When this deactivation occurs, the desired processing cannot be achieved. For example, when this deactivation occurs on a surface of a resist, a pleat-like irregular shape called "T-top" is formed in the case of a positive resist. Schematically indicated at 1 in FIG. 1A is a T-top formed like a roof on an upper surface of a resist pattern 2 which is to have a rectangular shape. In the case of a positive resist, when the deactivation occurs in a substrate to be processed, a blind over edging is formed. Likewise, schematically indicated at 2 in FIG. 2A is a blind over edging formed on a lower circumferential portion of a resist pattern 2 which is to have a rectangular shape. In the case of a negative resist, when the deactivation occurs on a surface of a resist, top rounding schematically indicated at 4 in FIG. 1B happens. In the case of a negative resist, when the deactivation occurs on a substrate, undercutting schematically indicated at 5 in FIG. 2B happens. In FIGS. 1 and 2, 6 is a substrate.
In order to avoid the above-mentioned problems, a variety of methods have been known. In one method, an amine or a neutralized substance (salt) of an amine and an acid is added to a resist in advance to supplement an acid deactivated [J. Photopolymer Science and Technology, vol. 8, #4 (1995) 535-542].
In this case, N-methylpyrrolidone (NMP) or amine phenol is added. However, NMP is not so effective. Since amine phenol shows a slight absorbance at a wavelength of 148 nm, it is sensitively disadvantageous in the KrF eximer laser lithography technology.